The mechanism is a pneumatic system, equipped with an indicator light, which changes the synchronization circuit and, hence, the direction of rotation of the main engine. The computer listing of the data recorder and the indicator light of the main engine rotation direction selector indicate that the lever of the engine telegraph in the engine-room was in fact placed in the astern position. However, the tachometer and the thrust of the propeller indicate that the main engine was turning in the ahead direction. It was reported that this failure of the mechanism was an isolated case, and that it had been reliable in the past. Subsequent tests did not indicate any malfunction.Analysis The mechanism is a pneumatic system, equipped with an indicator light, which changes the synchronization circuit and, hence, the direction of rotation of the main engine. The computer listing of the data recorder and the indicator light of the main engine rotation direction selector indicate that the lever of the engine telegraph in the engine-room was in fact placed in the astern position. However, the tachometer and the thrust of the propeller indicate that the main engine was turning in the ahead direction. It was reported that this failure of the mechanism was an isolated case, and that it had been reliable in the past. Subsequent tests did not indicate any malfunction. The main engine manoeuvres were controlled from the engine-room. The direction of rotation of the main engine is selected automatically when the engineer of the watch carries out the manoeuvring orders sent from the bridge via the engine telegraph. Although the main engine controls were set for astern, it was noticed shortly afterward that the engine was actually turning in the ahead direction. Subsequent tests of the engine telegraph mechanism in the control room did not indicate any malfunction.Findings The main engine manoeuvres were controlled from the engine-room. The direction of rotation of the main engine is selected automatically when the engineer of the watch carries out the manoeuvring orders sent from the bridge via the engine telegraph. Although the main engine controls were set for astern, it was noticed shortly afterward that the engine was actually turning in the ahead direction. Subsequent tests of the engine telegraph mechanism in the control room did not indicate any malfunction. The MIMI ran aground because of the unexpected thrust of the propeller in the ahead direction. Although the main engine was set for reverse rotation, it was noticed shortly afterward that it was turning in the ahead direction. The exact cause of the malfunction of the mechanism could not be determined.Causes The MIMI ran aground because of the unexpected thrust of the propeller in the ahead direction. Although the main engine was set for reverse rotation, it was noticed shortly afterward that it was turning in the ahead direction. The exact cause of the malfunction of the mechanism could not be determined. Subsequently, a service engineer from the engine manufacturer investigated the malfunction in the manoeuvring system. No error in the system was discovered. The malfunction has not re-occurred.Safety Action Taken Subsequently, a service engineer from the engine manufacturer investigated the malfunction in the manoeuvring system. No error in the system was discovered. The malfunction has not re-occurred.